(CNN)With every revelation in the Trump-Russia controversy it's becoming clear that the most important moment in Donald Trump's transition involved the man he seems to detest the most.

Two days after the election, Barack Obama delivered a face-to-face warning to Trump about the risk of keeping retired Gen. Michael Flynn around. Trump ignored the advice and instead invested maximum trust in Flynn as he made him national security adviser.

Obama's effort to save Trump and the nation from Flynn is full of painful irony. Remember, Trump is the man who spent years promoting racist conspiracy theories suggesting Obama was foreign-born and thus not legally qualified to be president. Flynn, whom Obama dismissed because of concerns about his leadership, then mocked Obama's ally, Hillary Clinton, with chants of "lock her up" during the campaign.

Obama could have stayed mum. A lesser man would have savored the knowledge that Trump and Flynn were headed for crisis. Obama did his duty by trying to help his successor.

The judgment Obama showed was typical for a president who, prior to politics, was an expert in constitutional law and understood his responsibilities to fulfill the oath he took to "preserve, protect and defend" it.

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In counseling Trump, Obama also acted in the best tradition of commanders in chief who must defend the nation against enemies foreign and domestic. Flynn was a potential threat to US security interests, and after eight years of defending the country Obama wasn't going to leave this threat unnamed.

Why didn't Trump heed Obama? To understand, it helps to understand his vain and dark perspective on life. Long ago Trump copped to being somewhat paranoid, explaining that "being a little bit paranoid isn't bad." He advised applying this fearful and delusional thinking "to people who are even close to you" because in the end, everyone acts out of self-interest.

This point of view explains why Trump values loyalty above other traits and, even then, tests those he supposedly trusts. It also explains why Trump couldn't take Obama's advice. He couldn't imagine Obama would set aside party, and the chance to see an opponent suffer, for the good of the country.

Trump's vanity is also a part of the problem. Certain of his own superiority, Trump believes in natural ability and values it above experience and character. He considers himself a great judge of talent. According to this logic, if he drew Flynn close to himself during the campaign -- and Flynn surely was one of his very top advisers/surrogates -- then he must be good.

Likewise, failing to reward him would suggest Trump had made a mistake. Trump hates to admit a mistake and he wasn't going to do it on the basis of advice from Obama.

Then there's Donald Trump's superficiality. The President considers himself to be a very good-looking man and he likes to surround himself with good-looking men and women. When he was putting together his government, aides spoke of how he wanted people who" looked the part" and thus, approached appointments like he was casting a movie.

Rex Tillerson, silver-haired and mature, looks like a Hollywood secretary of state. James Mattis, secretary of defense, is a trim and muscular man who looks like a commander. Trump also crowed about how he liked his nickname, Mad Dog.

In Flynn's case, Trump, stuck with the craggy-faced Army officer whose appearance suggests steadfast strength. It must be noted that Trump has a strange attachment to military men -- he calls them "my generals" -- and Flynn was likely the one he favored most despite all of the signs that he was not fit for a crucial and sensitive assignment.

Indeed, the mere fact that Flynn relished his role as a full-throated and caustic political campaigner showed he lacked the temperament to handle a top national security post. No serious spymaster would ever give the kind of soapbox performances Flynn gave in 2016. But Trump, whose formative years were spent at a military academy, was determined to keep him close.

Since Flynn was likely under surveillance, there's a good chance Trump was recorded in conversation with him during and after the campaign. Trump is a conspiratorial sort who loves to gossip and scheme. In the past, when his goals involved self-promotion and the accumulation of wealth, the risks in this behavior were limited and if he got into trouble his lawyers got him out of it.

Now, special counsel Robert Mueller, with the sort of firepower Trump has never faced before, is moving methodically in his investigation of Russian interference in the 2016 campaign and related issues. He has charged four Trump associates with serious crimes. Two, including Flynn, have pleaded guilty. Trump is responding as he always has, attempting to bully and denigrate and deny the truth.

Much of Trump's troubles could have been avoided if he had been able to heed the advice of a predecessor, Obama, whose experience and training as a lawyer would have enabled him to predict the miserable future Trump now inhabits. Blinded by his vanities, Trump couldn't see the gift Obama offered.

Editor's note: An earlier version of this article incorrectly said Michael Flynn is an ex-Marine; he is a retired Army officer.